Avoiding â€œMicrosoft Excelâ€ prompt

I'm writing the following bits of code for a SaveFile Dialog box in Visual Basic 2010.NET. The code works well as the XLSX file is created and opens in Microsoft Excel. However, the problem that I am having is that if the program overwrites a file, the user is getting two prompts. One prompt is from the program's own SaveFile dialog confirming the choice. The other is from Microsoft Excel asking you the same. It's as if the program is running in the background.

Does anyone know how I can write this code to save the file as an Excel file?